Etch Barrier Conductive Structures for Low-Loss Microelectronic Packaging
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Solution Overview
Problem
Surface roughness of conductive structures in electronic package substrates leads to increased resistivity and signal loss, particularly at high frequencies, due to impedance mismatch, while roughening is necessary for adhesion with dielectric layers, creating a tension between conductivity and adhesion.
Innovation Solution
Forming conductive structures with a surface roughness of 50 nm or less using a dose-selective dual development photoresist and a silicon nitride layer to improve adhesion without increasing signal loss, by creating a smooth surface and using an etch barrier to protect against subsequent processes that could roughen the surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the surface of the conductive structure is roughened to improve adhesion with dielectric layers, then adhesion strength is improved, but surface roughness increases leading to higher resistivity and signal loss
Solution Approach 1:
The solution segments the adhesion function from the conductive surface by introducing a separate adhesion layer. The adhesion layer is applied to the smooth conductive surface, decoupling the adhesion requirement from the conductive surface itself. This allows the conductive surface to remain smooth for low signal loss while the adhesion layer provides the necessary bonding strength to dielectric layers.
Solution Approach 2:
An adhesion layer serves as an intermediary between the smooth conductive structure and the dielectric layers. This intermediate layer mediates the adhesion requirement, allowing the conductive surface to maintain its smooth topology for optimal electrical performance while the adhesion layer provides the mechanical bonding function.
2Loss of energy
If a smooth surface is maintained on the conductive structure to reduce signal loss, then resistivity is reduced and signal transmission is improved, but adhesion with subsequent dielectric layers deteriorates
Solution Approach 1:
The solution segments the adhesion function from the conductive surface by introducing a separate adhesion layer. The adhesion layer is applied to the smooth conductive surface, decoupling the adhesion requirement from the conductive surface itself. This allows the conductive surface to remain smooth for low signal loss while the adhesion layer provides the necessary bonding strength to dielectric layers.
Solution Approach 2:
An adhesion layer serves as an intermediary between the smooth conductive structure and the dielectric layers. This intermediate layer mediates the adhesion requirement, allowing the conductive surface to maintain its smooth topology for optimal electrical performance while the adhesion layer provides the mechanical bonding function.
Data Source
AI summary
Conductive structures in a microelectronic package and having a surface roughness of 50 nm or less are described. This surface roughness is from 2 to 4 times less than can be found in packages with conductive structures (e.g., traces) formed using alternative techniques. This reduced surface roughness has a number of benefits, which in some cases includes a reduction of insertion loss and improves a signal to noise ratio for high frequency computing applications. The reduced surface roughness can be accomplished by protecting the conductive structure r during etch processes and applying an adhesion promoting layer to the conductive structure.